/*
 * jdcolor.c
 *
 * Copyright (C) 1991-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains output colorspace conversion routines.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private subobject */

typedef struct {
    struct jpeg_color_deconverter pub;/* public fields */

    /* Private state for YCC->RGB conversion */
    int *   Cr_r_tab;   /* => table for Cr to R conversion */
    int *   Cb_b_tab;   /* => table for Cb to B conversion */
    INT32 * Cr_g_tab;   /* => table for Cr to G conversion */
    INT32 * Cb_g_tab;   /* => table for Cb to G conversion */
} my_color_deconverter;

typedef my_color_deconverter * my_cconvert_ptr;


/**************** YCbCr -> RGB conversion: most common case **************/

/*
 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
 * The conversion equations to be implemented are therefore
 *	R = Y                + 1.40200 * Cr
 *	G = Y - 0.34414 * Cb - 0.71414 * Cr
 *	B = Y + 1.77200 * Cb
 * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
 *
 * To avoid floating-point arithmetic, we represent the fractional constants
 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
 * the products by 2^16, with appropriate rounding, to get the correct answer.
 * Notice that Y, being an integral input, does not contribute any fraction
 * so it need not participate in the rounding.
 *
 * For even more speed, we avoid doing any multiplications in the inner loop
 * by precalculating the constants times Cb and Cr for all possible values.
 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
 * for 12-bit samples it is still acceptable.  It's not very reasonable for
 * 16-bit samples, but if you want lossless storage you shouldn't be changing
 * colorspace anyway.
 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
 * values for the G calculation are left scaled up, since we must add them
 * together before rounding.
 */

#define SCALEBITS   16  /* speediest right-shift on some machines */
#define ONE_HALF    ( (INT32) 1 << ( SCALEBITS - 1 ) )
#define FIX( x )      ( (INT32) ( ( x ) * ( 1L << SCALEBITS ) + 0.5 ) )


/*
 * Initialize tables for YCC->RGB colorspace conversion.
 */

LOCAL void
build_ycc_rgb_table( j_decompress_ptr cinfo ) {
    my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
    int i;
    INT32 x;
    SHIFT_TEMPS

    cconvert->Cr_r_tab = (int *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( int ) );
    cconvert->Cb_b_tab = (int *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( int ) );
    cconvert->Cr_g_tab = (INT32 *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( INT32 ) );
    cconvert->Cb_g_tab = (INT32 *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( INT32 ) );

    for ( i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++ ) {
        /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
        /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
        /* Cr=>R value is nearest int to 1.40200 * x */
        cconvert->Cr_r_tab[i] = (int)
                                RIGHT_SHIFT( FIX( 1.40200 ) * x + ONE_HALF, SCALEBITS );
        /* Cb=>B value is nearest int to 1.77200 * x */
        cconvert->Cb_b_tab[i] = (int)
                                RIGHT_SHIFT( FIX( 1.77200 ) * x + ONE_HALF, SCALEBITS );
        /* Cr=>G value is scaled-up -0.71414 * x */
        cconvert->Cr_g_tab[i] = ( -FIX( 0.71414 ) ) * x;
        /* Cb=>G value is scaled-up -0.34414 * x */
        /* We also add in ONE_HALF so that need not do it in inner loop */
        cconvert->Cb_g_tab[i] = ( -FIX( 0.34414 ) ) * x + ONE_HALF;
    }
}


/*
 * Convert some rows of samples to the output colorspace.
 *
 * Note that we change from noninterleaved, one-plane-per-component format
 * to interleaved-pixel format.  The output buffer is therefore three times
 * as wide as the input buffer.
 * A starting row offset is provided only for the input buffer.  The caller
 * can easily adjust the passed output_buf value to accommodate any row
 * offset required on that side.
 */

METHODDEF void
ycc_rgb_convert( j_decompress_ptr cinfo,
                 JSAMPIMAGE input_buf, JDIMENSION input_row,
                 JSAMPARRAY output_buf, int num_rows ) {
    my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
    register int y, cb, cr;
    register JSAMPROW outptr;
    register JSAMPROW inptr0, inptr1, inptr2;
    register JDIMENSION col;
    JDIMENSION num_cols = cinfo->output_width;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    register int * Crrtab = cconvert->Cr_r_tab;
    register int * Cbbtab = cconvert->Cb_b_tab;
    register INT32 * Crgtab = cconvert->Cr_g_tab;
    register INT32 * Cbgtab = cconvert->Cb_g_tab;
    SHIFT_TEMPS

    while ( --num_rows >= 0 ) {
        inptr0 = input_buf[0][input_row];
        inptr1 = input_buf[1][input_row];
        inptr2 = input_buf[2][input_row];
        input_row++;
        outptr = *output_buf++;
        for ( col = 0; col < num_cols; col++ ) {
            y  = GETJSAMPLE( inptr0[col] );
            cb = GETJSAMPLE( inptr1[col] );
            cr = GETJSAMPLE( inptr2[col] );
            /* Range-limiting is essential due to noise introduced by DCT losses. */
            outptr[RGB_RED] =   range_limit[y + Crrtab[cr]];
            outptr[RGB_GREEN] = range_limit[y +
                                            ( (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr],
                                                                 SCALEBITS ) )];
            outptr[RGB_BLUE] =  range_limit[y + Cbbtab[cb]];
            outptr += RGB_PIXELSIZE;
        }
    }
}


/**************** Cases other than YCbCr -> RGB **************/


/*
 * Color conversion for no colorspace change: just copy the data,
 * converting from separate-planes to interleaved representation.
 */

METHODDEF void
null_convert( j_decompress_ptr cinfo,
              JSAMPIMAGE input_buf, JDIMENSION input_row,
              JSAMPARRAY output_buf, int num_rows ) {
    register JSAMPROW inptr, outptr;
    register JDIMENSION count;
    register int num_components = cinfo->num_components;
    JDIMENSION num_cols = cinfo->output_width;
    int ci;

    while ( --num_rows >= 0 ) {
        for ( ci = 0; ci < num_components; ci++ ) {
            inptr = input_buf[ci][input_row];
            outptr = output_buf[0] + ci;
            for ( count = num_cols; count > 0; count-- ) {
                *outptr = *inptr++;/* needn't bother with GETJSAMPLE() here */
                outptr += num_components;
            }
        }
        input_row++;
        output_buf++;
    }
}


/*
 * Color conversion for grayscale: just copy the data.
 * This also works for YCbCr -> grayscale conversion, in which
 * we just copy the Y (luminance) component and ignore chrominance.
 */

METHODDEF void
grayscale_convert( j_decompress_ptr cinfo,
                   JSAMPIMAGE input_buf, JDIMENSION input_row,
                   JSAMPARRAY output_buf, int num_rows ) {
    jcopy_sample_rows( input_buf[0], (int) input_row, output_buf, 0,
                       num_rows, cinfo->output_width );
}


/*
 * Adobe-style YCCK->CMYK conversion.
 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
 * conversion as above, while passing K (black) unchanged.
 * We assume build_ycc_rgb_table has been called.
 */

METHODDEF void
ycck_cmyk_convert( j_decompress_ptr cinfo,
                   JSAMPIMAGE input_buf, JDIMENSION input_row,
                   JSAMPARRAY output_buf, int num_rows ) {
    my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
    register int y, cb, cr;
    register JSAMPROW outptr;
    register JSAMPROW inptr0, inptr1, inptr2, inptr3;
    register JDIMENSION col;
    JDIMENSION num_cols = cinfo->output_width;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    register int * Crrtab = cconvert->Cr_r_tab;
    register int * Cbbtab = cconvert->Cb_b_tab;
    register INT32 * Crgtab = cconvert->Cr_g_tab;
    register INT32 * Cbgtab = cconvert->Cb_g_tab;
    SHIFT_TEMPS

    while ( --num_rows >= 0 ) {
        inptr0 = input_buf[0][input_row];
        inptr1 = input_buf[1][input_row];
        inptr2 = input_buf[2][input_row];
        inptr3 = input_buf[3][input_row];
        input_row++;
        outptr = *output_buf++;
        for ( col = 0; col < num_cols; col++ ) {
            y  = GETJSAMPLE( inptr0[col] );
            cb = GETJSAMPLE( inptr1[col] );
            cr = GETJSAMPLE( inptr2[col] );
            /* Range-limiting is essential due to noise introduced by DCT losses. */
            outptr[0] = range_limit[MAXJSAMPLE - ( y + Crrtab[cr] )];/* red */
            outptr[1] = range_limit[MAXJSAMPLE - ( y +  /* green */
                                                  ( (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr],
                                                                       SCALEBITS ) ) )];
            outptr[2] = range_limit[MAXJSAMPLE - ( y + Cbbtab[cb] )];/* blue */
            /* K passes through unchanged */
            outptr[3] = inptr3[col];/* don't need GETJSAMPLE here */
            outptr += 4;
        }
    }
}


/*
 * Empty method for start_pass.
 */

METHODDEF void
start_pass_dcolor( j_decompress_ptr cinfo ) {
    /* no work needed */
}


/*
 * Module initialization routine for output colorspace conversion.
 */

GLOBAL void
jinit_color_deconverter( j_decompress_ptr cinfo ) {
    my_cconvert_ptr cconvert;
    int ci;

    cconvert = (my_cconvert_ptr)
               ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                            SIZEOF( my_color_deconverter ) );
    cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
    cconvert->pub.start_pass = start_pass_dcolor;

    /* Make sure num_components agrees with jpeg_color_space */
    switch ( cinfo->jpeg_color_space ) {
        case JCS_GRAYSCALE:
            if ( cinfo->num_components != 1 ) {
                ERREXIT( cinfo, JERR_BAD_J_COLORSPACE );
            }
            break;

        case JCS_RGB:
        case JCS_YCbCr:
            if ( cinfo->num_components != 3 ) {
                ERREXIT( cinfo, JERR_BAD_J_COLORSPACE );
            }
            break;

        case JCS_CMYK:
        case JCS_YCCK:
            if ( cinfo->num_components != 4 ) {
                ERREXIT( cinfo, JERR_BAD_J_COLORSPACE );
            }
            break;

        default:    /* JCS_UNKNOWN can be anything */
            if ( cinfo->num_components < 1 ) {
                ERREXIT( cinfo, JERR_BAD_J_COLORSPACE );
            }
            break;
    }

    /* Set out_color_components and conversion method based on requested space.
     * Also clear the component_needed flags for any unused components,
     * so that earlier pipeline stages can avoid useless computation.
     */

    switch ( cinfo->out_color_space ) {
        case JCS_GRAYSCALE:
            cinfo->out_color_components = 1;
            if ( ( cinfo->jpeg_color_space == JCS_GRAYSCALE ) ||
                ( cinfo->jpeg_color_space == JCS_YCbCr ) ) {
                cconvert->pub.color_convert = grayscale_convert;
                /* For color->grayscale conversion, only the Y (0) component is needed */
                for ( ci = 1; ci < cinfo->num_components; ci++ ) {
                    cinfo->comp_info[ci].component_needed = FALSE;
                }
            } else {
                ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL );
            }
            break;

        case JCS_RGB:
            cinfo->out_color_components = RGB_PIXELSIZE;
            if ( cinfo->jpeg_color_space == JCS_YCbCr ) {
                cconvert->pub.color_convert = ycc_rgb_convert;
                build_ycc_rgb_table( cinfo );
            } else if ( cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3 ) {
                cconvert->pub.color_convert = null_convert;
            } else {
                ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL );
            }
            break;

        case JCS_CMYK:
            cinfo->out_color_components = 4;
            if ( cinfo->jpeg_color_space == JCS_YCCK ) {
                cconvert->pub.color_convert = ycck_cmyk_convert;
                build_ycc_rgb_table( cinfo );
            } else if ( cinfo->jpeg_color_space == JCS_CMYK ) {
                cconvert->pub.color_convert = null_convert;
            } else {
                ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL );
            }
            break;

        default:
            /* Permit null conversion to same output space */
            if ( cinfo->out_color_space == cinfo->jpeg_color_space ) {
                cinfo->out_color_components = cinfo->num_components;
                cconvert->pub.color_convert = null_convert;
            } else {/* unsupported non-null conversion */
                ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL );
            }
            break;
    }

    if ( cinfo->quantize_colors ) {
        cinfo->output_components = 1;
    }                             /* single colormapped output component */
    else {
        cinfo->output_components = cinfo->out_color_components;
    }
}
